Enhanced ultrasound penetrates bone and metal:

Researchers from North Carolina State University have developed a technique that allows ultrasound to penetrate bone or metal, using customised structures that offset the distortion usually caused by so-called aberrating layers.

‘We’ve designed complementary metamaterials that will make it easier for medical professionals to use ultrasound for diagnostic or therapeutic applications, such as monitoring blood flow in the brain or to treat brain tumours,’ said Tarry Chen Shen, a Ph.D. student at NC State and lead author of a paper on the work. ‘This has been difficult in the past because the skull distorts the ultrasound’s acoustic field.’

‘These metamaterials could also be used in industrial settings,’ said Dr. Yun Jing, an assistant professor of mechanical and aerospace engineering at NC State and senior author of the paper. ‘For example, it would allow you to use ultrasound to detect cracks in airplane wings under the wing’s metal ‘skin.’’

Ultrasound imaging works by emitting high frequency acoustic waves. When those waves rebound off an object, they return to the ultrasound equipment, which translates the waves into an image.

Some materials such as bone or metal have physical characteristics that block or distort ultrasound’s acoustic waves and these materials are called aberrating layers. The researchers are said to have addressed this problem by designing customised metamaterial structures that take into account the acoustic properties of the aberrating layer and offsetting them. The metamaterial structure uses a series of membranes and small tubes to achieve the desired acoustic characteristics.

Source: The Engineer
Posted by: Er_sanch.

THE UPA-VEDAS AND VEDANGAS

Aside from the Upanishads, there are also the Upa-vedas. These are the Artha-veda (science of economics and sociology), the Dhanur-veda (the science of defense, war, and politics), the Gandharva-veda (art of music, dancing, and singing), and Ayurveda (the holistic medical science). These are smaller compositions, each are attached to one of the four main samhitas (namely the Rig, Yajur, Sama, and Atharva respectively). Unfortunately, most of these compositions are difficult to find, except for the Ayurveda, the majority of which is still available but not all of its original text.

These are a part of the eighteen principal branches of Vedic knowledge, which, according to the Vishnu Purana, are listed with their sources as the six Vedangas:

The four Vedas, the six Angas (or subsidiary portions of the Vedas), viz., Siksha, rules of reciting the prayers, the accents, and tones to be observed; Kalpa, ritual; Vyakarana, grammar; Nirukta, glossarial comment; Chandas, metre; and Jyotish, astronomy; with Mimamsa, theology; Nyaya, logic; Dharma, the institutes of law; and the Puranas, constitute the fourteen principal branches of knowledge. Or they are considered as eighteen with the addition of these four: the Ayur-veda, medical science as taught by Lord Dhanvantari; Dhanur-veda, the science of archery or military arms taught by Bhrigu; Gandharva-veda, or drama and the arts of music, dancing, etc., of which the Muni Bharata was the author; and the Artha sastram, or science of government, as laid down first by Brihaspati. (Vishnu Purana, Book Three, Chapter Six)

To briefly explain some of the branches mentioned above:

Vyakarana is the science of Sanskrit grammar. This is presently based on the Panini grammar, since the other ancient forms or books are extinct. The Panini system, which has some 4000 sutras, is said to have been inspired by Lord Shiva when he once played on his small damru drum from which came 14 separate sounds. Those vibrations inspired Panini, who then explained the science of Sanskrit grammar. These vibrations were said to be originally in the mysterious formula of the Maheshvara Sutra. This Sutra is said to contain all sounds arranged in an order that holds the key to all structure of language.

Panini also provided the dhatu path, which is a dictionary of the root Sanskrit words. Then he gave the unadi sutras to describe how the words in the original Vedic samhitas (the four Vedas) were formed, which can provide the means of understanding the real definition of the words in the samhita mantras. Without this, it is easy for a person to mistranslate the real meaning or purpose of the Vedic mantras.

Nirukta provides the explanations of the Vedic words. It is used along with the Nighantu, which is a collection of Vedic words with their basic explanations. These are used with the Vyakarana to understand the exact meaning of Sanskrit words to make sure the Vedic samhita mantras are not misunderstood.

Siksha is the science of correct pronunciation of Vedic mantras, such as intonation, duration, and the accent on a word or syllable. This will determine how one “sings” each mantra. Differences in the pronunciation of a mantra can also change its meaning, and the outcome of the ritual. That is one of the reasons why the old Vedic rituals are no longer recommended for this day and age. The problem is that this is difficult to learn and almost all books on the topic have become lost.

Chandas is the science of correctly emphasizing the meter of the Vedic verses according to the division or parts and letters, and the correct pronunciation of the words. The Vedic mantras are also named according to its parts. For example, the anushtup chand is a mantra of four parts in one stanza, and with 32 letters. Yet if it has 31 letters in four parts, it is called brihati chand, and so on.

Jyotish is the science of Vedic astrology. This was used for a couple of reasons. Primarily it was for establishing the correct position of the stars and planets at certain times, such as one’s birth, and their effects for predicting one’s future life. It was also for calculating the best times to begin special activities, such as Vedic rituals. There were many books on jyotish, but most have now become lost, leaving but several left to study.

The Artha-sastram is said to have been established first by Brihaspati, but was written most recently by Kautilya in the fourth century BC for the king, Chandragupta Maurya. It is the science of government and economics that takes credit for some of the principles of corporate management that have gained popularity today, such as using prabhu shakti (vision), mantra shakti (mission), and utsah shakti (motivation).

Love Letters from Ancient India

Letter writing has a long history in ancient India. We have a number of references to letters particularly written by women. Vidharba princess Rukmini wrote a love letter to Lord Krishna requesting him to marry her. Sanskrit epic poem Sisupalawadha refers to it. We have two letter verses in the Prakrit anthology Gatha Sapta sati.

Kalidasa, the greatest of the Sanskrit poets, mentions letter writing in his play Vikrama Urvasiyam. Kalidasa lived around 1st century BC. King Pururavas falls in love with a celestial nymph named Urvashi. After writing her mortal suitor a love letter on a birch leaf, Urvashi returns to the heavens to perform in a celestial play. However, she is so smitten that she misses her cue and pronounces her lover’s name during the performance. As a punishment for ruining the play, Urvashi is banished from heaven.

Letter writing was an integral part of our culture. We have a sculpture of a beautiful lady writing a letter in Khajuraho Khandariya Mahadev temple. Needless to say it is a love letter. Damayanthi sent a riddle in a poem to find her husband King Nalan. Bhoja sent a riddle in a poem to find the great poet Kalaidas. Probably these were also sent in letter format.

Tamil letter

In Silappadikaram, one of the five Tamil epics, we have references to several letters. Madhavi, the dancer with whom Kovalan had relationship for sometime wrote to him after separation. She asked him why he left her. It was sent through a Brahmin. In ancient India Brahmins acted as messengers for kings and others.

Madhavi sent the letter to Kovalan through a Brahmin called Kausikan. Kausikan narrated to Kovalan how he got it from her. “Madhavi wrote this letter on a palm leaf with her tender hands and sealed it. She requested me to hand it over to you”. When Kovalan opened the letter, he found the following words: My lord, I fall at your feet. Kindly forgive my indiscreet words. What is my mistake which made you leave the city during the night with your wife of noble birth, even without the knowledge of your parents? My mind suffers in ignorance. Please clarify. O great and true one of wisdom, may you bless me (This is from Puranceri Irutta Katai in Silappadikaram).

When Kovalan finished reading it, he gave the letter back to Kausikn and requested him to show it to his parents so that they would also know what happened. Kovalam told him that it was his fault.

In another place (Ataikala Katai), a story of Panchatantra Tales is referred to. A Brahmin lady who raised a mongoose went out to fetch water leaving the care of her baby to the mongoose. In those days people were afraid of snake bites and so raised mongooses, the enemies of the snakes. As expected a snake came near the child and the mongoose killed the snake and protected her child. Mongoose was waiting at the gate to give the good news. But Alas! When the woman saw the blood in the mouth of the mongoose she thought it killed her child and threw her water pot on the head of the mongoose. It had an instant death.

Her husband was enraged by her hasty stupid act. Immediately he gave her a palm leaf containing a message in Sanskrit. He told her that he wouldn’t eat food served by her. He went on a pilgrimage to North. When Kovalan saw that distressed lady he took the message from her and performed several rituals to absolve her from the sin. He also brought her husband back. This is narrated by another Brahmin called Matalan. He reminded all the good deeds done by Kovalan and wondered what caused the present misery.

It bears testimony to the fact that Kovalan possessed a sound knowledge of Sanskrit. We can also conclude that letter writing was common and women were able to write freely. Sanskrit was used for writing letters in the first century AD. Though Silappadikaram was written around fifth century AD, the incident happened in the first century.

Lord Shiva’s Recommendation Letter

Writing recommendation letters to political leaders for favours is the order of the day. But according to Tamil books, Lord Shiva was the one who started this custom. When a Northern singer known as Hemnath came to Pandya country and challenged the Tamil singers Lord Shiva helped his devotee Bababathran, the royal singer, by scaring away Hemnath. The northern singer ran away in the night after hearing Banabathran’s worst student, who was none else but Shiva. He thought if the worst one can sing this good, Banabathran must be better than him. So the singer bolted away with his disciples at the dead of night. After this incident, Banabathran went to work in the temple and suffered from poverty. Shiva came in the disguise of a Tamil saint and gave him a recommendation letter to the king of Chera country who was a great devotee of Shiva. He alerted Chera king in a dream that Bana was coming with a letter. Chera welcomed him and gave him lot of money. The letter is in verse form and says that Bana is also a great devotee like the Chera king and he must be helped with money